This invention relates to a brake apparatus for a supply reel containing a cable or the like, and more particularly to a disc brake assembly embodying a construction of parts whereby the brake pads are normally maintained out of contact with the disc until acted upon by fluid pressure and wherein unlatching of brake housing parts facilitates replacement of an emptied supply reel.
It is the usual practice by utility companies to transport cable used to transmit electrical power and telephone communication on relatively large supply reels to a job site. The reel is usually supported by saddles on pedestals for rotation so that the cable can be drawn from the reel. Some form of brake apparatus is desirable, if not actually required, to control rotation, overspinning and surging of the reel as the cable is paid out. Overspinning is an unwinding of an unwanted length of coil which can be controlled to some extent by the speed at which the cable is pulled from the reel. Surging developes from the elasticity of the pulling cable and can destroy the cable "eye" used for pulling. It is a time consuming and laborious operation to rewind a length of cable that has been unintentionally uncoiled simply because rotation of the reel cannot be stopped. Many times, as the cable is being payed-out, a workman is below the supply reel in the manhole guiding the cable. If the reel should overspin, he could be injured. Moreover, a surge control is needed to prevent damage due to shock.
The present invention is designed to overcome these problems as well as others which arise when it is desired to utilize a brake apparatus to control rotation of a supply reel for a cable. The brake apparatus must, of course, be an economical capital investment and at the same time the apparatus must be constructed in such a manner so as to facilitate the substitution of an emptied reel with one containing a supply of cable. The energy which must be dissipated in the form of heat generated by the brake device is relatively large because of the size and weight of the storage reel. Even when a disc-brake principle is employed according to the present invention, it has been discovered that efficient braking can only be achieved by avoiding continuous frictional engagement by the brake pads with the rotor. Therefore, one of the basic concepts of the present invention is that frictional contact should only exist between the disc and the brake pads during the actual braking mode of operation. In less efficient types of brake devices, such as a band-type brake, excessive quantities of heat are developed very rapidly, producing poor and inefficient braking that is unacceptable for controlling the rotation of the massive cable storage reel.